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In Vitro Bioactivity and Biocompatibility of Bio-Inspired Ti-6Al-4V Alloy Surfaces Modified by Combined Laser Micro/Nano Structuring
摘要： The bioactivity and biocompatibility play key roles in the success of dental and orthopaedic implants. Although most commercial implant systems use various surface microstructures, the ideal multi-scale topographies capable of controlling osteointegration have not yielded conclusive results. Inspired by both the isotropic adhesion of the skin structures in tree frog toe pads and the anisotropic adhesion of the corrugated ridges on the scales of Morpho butter?y wings, composite micro/nano-structures, including the array of micro-hexagons and oriented nano-ripples on titanium alloy implants, were respectively fabricated by microsecond laser direct writing and femtosecond laser-induced periodic surface structures, to improve cell adherence, alignment and proliferation on implants. The main di?erences in both the bioactivity in simulated body ?uid and the biocompatibility in osteoblastic cell MC3T3 proliferation were measured and analyzed among Ti-6Al-4V samples with smooth surface, micro-hexagons and composite micro/nano-structures, respectively. Of note, bioinspired micro/nano-structures displayed the best bioactivity and biocompatibility after in vitro experiments, and meanwhile, the nano-ripples were able to induce cellular alignment within the micro-hexagons. The reasons for these di?erences were found in the topographical cues. An innovative functionalization strategy of controlling the osteointegration on titanium alloy implants is proposed using the composite micro/nano-structures, which is meaningful in various regenerative medicine applications and implant ?elds.
关键词： bioinspired surfaces,biocompatibility,cell adherence,femtosecond laser,bioactivity,cell alignment,Ti-6Al-4V,LIPSS
更新于2025-09-19 17:13:59
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Laser Induced Periodic Surface Structure Enhances Neuroelectrode Charge Transfer Capabilities and Modulates Astrocyte Function
摘要： The brain machine interface (BMI) describes a group of technologies capable of communicating with excitable nervous tissue within the central nervous system (CNS). BMI’s have seen major advances in recent years but these advances have been impeded due to a temporal deterioration in the signal to noise ratio of recording electrodes following insertion into the CNS. This deterioration has been attributed to an intrinsic host tissue response, namely reactive gliosis which involves a complex series of immune mediators resulting in implant encapsulation via the synthesis of pro-inflammatory signaling molecules and the recruitment of glial cells. There is a clinical need to reduce tissue encapsulation in situ and improve long-term neuroelectrode functionality. Physical modification of the electrode surface at the nanoscale could satisfy these requirements by integrating electrochemical and topographical signals to modulate neural cell behavior. In this study, commercially available platinum iridium (Pt/Ir) microelectrode probes were nanotopographically (NT) functionalized using femto/picosecond laser processing to generate laser induced periodic surface structures (LIPSS). Three different topographies and their physical properties were assessed by scanning electron microscopy and atomic force microscopy. The electrochemical properties of these interfaces were investigated using electrochemical impedance spectroscopy and cyclic voltammetry. The in vitro response of mixed cortical cultures (embryonic rat E14/E17), was subsequently assessed by confocal microscopy, ELISA and multiplex protein array analysis. Overall LIPSS features improved the electrochemical properties of the electrodes, promoted cell alignment and modulated the expression of multiple ion channels involved in key neuronal functions.
关键词： astrogliosis,electrochemical impedance,platinum/iridium,neuroelectrode,cell alignment,LIPSS
更新于2025-09-16 10:30:52
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Wettability analysis of water on metal/semiconductor phases selectively structured with femtosecond laser-induced periodic surface structures
摘要： Femtosecond (fs) laser-induced periodic surface structures (LIPSS) were selectively generated on the surface of an Ag-Si alloy consisting of a metallic and a semiconducting phase. For this purpose, the alloy was irradiated with linearly polarized fs-laser pulses (τ = 300 fs, λ = 1025 nm, frep = 100 kHz) using a laser peak fluence F = 0.30 J/cm2. Due to the different light absorption behavior of the semiconductor (Si) and the metal (Ag) phase that results in different ablation thresholds of the respective phase, pronounced LIPSS with a period of Λ ≈ 950 nm and a modulation depth of h ≈ 220 nm were generated solely on the Si phase. The alloy surface was characterized by scanning electron microscopy, optical microscopy, white light interference microscopy and atomic force microscopy before and after laser irradiation. Chemical analysis was carried out by energy dispersive X-ray spectroscopy, revealing surface oxidation of the Si phase and no laser-induced chemical modification of the Ag phase. The surface wettability of the alloy was evaluated with distilled water and compared to the single constituents of the composites. After fs-laser irradiation, the surface is characterized by a reduced hydrophilic water contact angle. Furthermore, the alloy selectively structured with LIPSS revealed a droplet shape change due to the distinctly different contact angles on the Si (θ = 5°) and the Ag (θ = 74°) phase. This phenomenon was evaluated and discussed by local contact angle analyses using a confocal laser scanning microscope and a Rhodamine B dye. In addition, it was shown that the shape change due to different contact angles of the components allowed a targeted droplet movement on a macroscopic material boundary (Ag/Si) of the alloy. Selectively structured metal/semiconductor surfaces might be of particular interest for microfluidic devices with a directional droplet movement and for fundamental research of wettability.
关键词： Contact angle,Wettability,Microfluidic devices,LIPSS,Ag-Si alloy,Femtosecond laser
更新于2025-09-12 10:27:22
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Fabrication of Tuned Lipss-Based Metallic Polarization Gratings
摘要： Surface nanostructuring has received increasing attention in recent years due to the wide range of applications in which it offers advantages. Particularly, Laser-Induced Periodic Surface Structures (LIPSS) have proven useful for surface functionalization [1]. LIPSS are periodic formations generated in most materials when irradiated with linearly polarized radiation. The orientation of these structures is directly linked to the polarization of the incident light, while other parameters of their morphology such as period and depth can be controlled with the number of pulses, fluence, wavelength and pulse duration of the incident light. Due to their periodic nature, LIPSS behave optically as nanogratings [2], which have been largely studied as polarization converters (or Polarization Gratings, PGs). PGs are structures that introduce a phase shift in the incident light, which produces a change in its polarization state [3]. Therefore, PGs have potential applications as reflective waveplates [4], showing advantages over transmission waveplates such as higher damage thresholds and a lower temporal dispersion of the pulse. So far, PGs have been fabricated with methods such as direct laser interference or lithography [5]. The main drawbacks of these methods include limited choice of periods for the generated structures or a complex and environmentally unfriendly fabrication process, which could be overcome by a fabrication method based on LIPSS. In order to fabricate LIPSS-based PGs, stainless steel samples were irradiated with a 800 nm femtosecond Ti:Sapphire laser. The laser was focused onto the surface of the sample through a cylindrical lens with a focal length of 10 cm. The sample was translated perpendicular to the laser beam with a mechanical stage at a constant speed, generating LIPSS in a large area of 5 mm x 5 mm in a few seconds. By varying the fluence of the beam and the speed of the stage, LIPSS with different parameters were fabricated. Topography of the samples were characterized with AFM and SEM (Fig. 1a) microscopes, and polarization conversion and reflectivity were examined with a polarimeter. Results show that a gradual change in LIPSS morphology is associated to a gradual change in the ellipticity of the laser beam (Fig. 1b). It is also observed that LIPSS geometry changes smoothly with processing parameters. Therefore, it is proven that LIPSS-based PGs can be fabricated experimentally, and that the properties of such PGs can be tuned changing the LIPSS geometry, as expected. These results are in good agreement with the performed FDTD simulations for different LIPSS morphologies.
关键词： Surface nanostructuring,Polarization Gratings,LIPSS,Polarization conversion,Femtosecond laser
更新于2025-09-12 10:27:22
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Femtosecond laser shock peening of galvanized stainless steel
摘要： In this paper a SUS316L stainless steel was electroplated with metallic layers and coated with polymer films. A sub-100fs ultrashort laser pulse with a central wavelength of λ=800nm was utilized to process the layer. The aim was to generate shock waves due to ablation of the deposited sacrificial layers. Generated shockwaves propagate and penetrate the lower stainless-steel sample and increase its mechanical hardness (Laser Shock Peening). The sacrificial layer protects the sample from ablation damage and determines the shock wave coupling. To achieve maximal peening, we compare different sacrificial layers and laser processing parameters.
关键词： Ultrashort Laser Peening,Shock hardening,LIPSS,Laser Shock Peening
更新于2025-09-12 10:27:22
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Influence of processing parameters on characteristics of laser-induced periodic surface structures on steel and titanium
摘要： Laser-induced periodic surface structures (LIPSS) can appear due to interaction between polarized laser pulses and surface. They can be used to improve or change the surface functionality. Here, titanium and steel surfaces were irradiated by linearly polarized, 30-ps-laser pulses (wavelength of λ=1064 nm) and 45-ns-laser pulses (wavelength of λ=1060 nm), respectively. We investigated how pulse fluence, number of pulses, and pre-existing defects influence LIPSS formation and period. The results show that fluences lower than single-pulse fluence threshold for ablation lead to LIPSS with periods within 150-500 nm, while increased fluence results in larger spatial period between 800-1100 nm. A slight change in processing parameters can also result in different topographical and/or chemical characteristics of the top surface layer, making LIPSS undetectable by SEM.
关键词： laser nanostructuring,laser surface engineering,LIPSS,laser processing
更新于2025-09-12 10:27:22
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Tribological performance of metal-reinforced ceramic composites selectively structured with femtosecond laser-induced periodic surface structures
摘要： The impact of femtosecond (fs) laser-induced periodic surface structures (LIPSS) on tribological properties was investigated for metal-reinforced ceramic composites (Al2O3-ZrO2-Nb). For this purpose, the metallic niobium (Nb) phase was selectively structured with LIPSS in an air environment with different values of the fs-laser peak fluence by near-infrared fs-laser radiation (λ = 1,025 nm, τ = 300 fs, frep = 1 kHz), taking advantage of the different light absorption behavior of ceramic and metal. The tribological performance was evaluated by reciprocating sliding tests in a ball-on-disc configuration using Ringer’s solution as lubricant. The surfaces were characterized before and after laser irradiation by optical microscopy, scanning electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy, energy dispersive X-ray spectroscopy and by measuring the contact angle with Ringer’s solution. The LIPSS formation resulted in an increased wetting of the surface with the lubricant. Moreover, the selectively structured composite surfaces revealed a coefficient of friction significantly reduced by a factor of ~ 3 when compared to the non-irradiated surface. Furthermore, the formation of a laser-induced oxidation layer was detected with NbO as the most prominent oxidation state. Selectively structured composites with outstanding mechanical properties and enhanced tribological performance are of particular interest for biomedical applications.
关键词： femtosecond laser-induced periodic surface structures (LIPSS),tribology,wettability,ceramic matrix composites,coefficient of friction,selective surface structuring
更新于2025-09-12 10:27:22
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Influence of surface plasmon polaritons on laser energy absorption and structuring of surfaces
摘要： The accurate calculation of laser energy absorption during femto- or picosecond laser pulse experiments is very important for the description of the formation of periodic surface structures. On a rough material surface, a crack or a step edge, ultrashort laser pulses can excite surface plasmon polaritons (SPP), i.e. surface plasmons coupled to a laser-electromagnetic wave. The interference of such plasmon wave and the incoming pulse leads to a periodic modulation of the deposited laser energy on the surface of the sample. In the present work, within the frames of a Two Temperature Model we propose the analytical form of the source term, which takes into account SPP excited at a step edge of a dielectric-metal interface upon irradiation of an ultrashort laser pulse at normal incidence. The influence of the laser pulse parameters on energy absorption is quantified for the example of gold. This result can be used for nanophotonic applications and for the theoretical investigation of the evolution of electronic and lattice temperatures and, therefore, of the formation of surfaces with predestined properties under controlled conditions.
关键词： Laser energy absorption,Surface plasmon polaritons,Plasmonics,LIPSS,Ultrashort laser pulses
更新于2025-09-11 14:15:04
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Influence of Femtosecond Laser Surface Nanotexturing on the Friction Behavior of Silicon Sliding Against PTFE
摘要： The aim of the present work was to investigate the influence of laser-induced periodic surface structures (LIPSS) produced by femtosecond laser on the friction behavior of silicon sliding on polytetrafluoroethylene (PTFE) in unlubricated conditions. Tribological tests were performed on polished and textured samples in air using a ball-on-flat nanotribometer, in order to evaluate the friction coefficient of polished and textured silicon samples, parallel and perpendicularly to the LIPSS orientation. In the polished specimens, the friction coefficient decreases with testing time at 5 mN, while it increases slightly at 25 mN. It also decreases with increasing applied load. For the textured specimens, the friction coefficient tends to decrease with testing time in both sliding directions studied. In the parallel sliding direction, the friction coefficient decreases with increasing load, attaining values similar to those measured for the polished specimen, while it is independent of the applied load in the perpendicular sliding direction, exhibiting values lower than in the two other cases. These results can be explained by variations in the main contributions to friction and in the wear mechanisms. The influence of the temperature increase at the interface and the consequent changes in the crystalline phases of PTFE are also considered.
关键词： silicon,laser surface texturing,friction,LIPSS,PTFE,laser-induced periodic surface structures
更新于2025-09-11 14:15:04
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Femtosecond laser-induced large area of periodic structures on chalcogenide glass via twice laser direct-writing scanning process
摘要： We presented a theoretical and experimental study for the evolution of femtosecond laser direct-writing induced large area of periodic surface structures on As2S3 glass. The laser direct-writing induced large area of low spatial frequency LIPSS (LSFL) structures can be fabricated with the overlap rate increases from 65% to 80%. The evolution process can be defined by the competition between the laser fluence and pulse overlap rate. What is more important is that, based on secondary femtosecond laser scanning process, the interaction between the initial LSFL structures induced by the first scanning and the laser pulse of the second scanning process can induce local field enhancement effect, which can directly split the surface periodic structures of LSFL. Such new sub-sequent high spatial frequency LIPSS (HSFL) fabrication process is quite different from the traditional multi-pulse induced HSFL and can be used to fabricate large-area HSFL structures.
关键词： Nano-fabrication,Femtosecond laser,LIPSS,Chalcogenide glasses
更新于2025-09-11 14:15:04